Simulation of AlGaN/GaN MISFET With 3.6-GW/cm2 High FOM by SIPOS Field Plates Electric Field Modulation

In this article, a novel vertical trench gate AlGaN/GaN metal–insulator–semiconductor field-effect transistor (MISFET) with semi-insulating polycrystalline silicon (SIPOS) field plates [SIPOS vertical trench gate AlGaN/GaN (VT-AlGaN/GaN) MISFET] is proposed for the first time. In the OFF-state, the electric field distribution in the n-GaN buffer is more uniform due to the presence of SIPOS field plates and deep trench structure, and the breakdown voltage (BV) is increased. Simulation results using Technology Computer-Aided Design (TCAD) Sentaurus show that under the same n-GaN buffer layer thickness ( $7~\mu \text{m}$ ), the BVs of SIPOS VT-AlGaN/GaN MISFET and conventional vertical trench gate AlGaN/GaN MOSFET (conv.VT-AlGaN/GaN MOSFET) are 1828 and 1506 V, which increased 17.6%. In the ON-state, a majority carrier accumulation layer is formed on the surface between the n-GaN buffer and the thin Al2O3 layer. This high concentration electron region is equivalent to local high concentration doping region, and the specific ON-resistance ( ${R}_{ \rm{ON,sp}}$ ) of the device is greatly reduced. When the BV remains almost the same (1500 V), ${R}_{ \rm{ON,sp}}$ of SIPOS VT-AlGaN/GaN MISFET and conv.VT-AlGaN/GaN MOSFET is 0.63 and 1.03 $\text{m}\Omega \cdot \text {cm}^{{2}}$ , respectively. ${R}_{ \rm{ON,sp}}$ decreased by 38.8%. The maximum figures of merit (FOMs) of the SIPOS-vertical AlGaN/GaN MISFET and conv.VT-AlGaN/ GaN MOSFET are 3.6 and 2.4 GW/cm2, respectively. The proposed SIPOS VT-AlGaN/GaN MISFET achieves a better compromise between BV and ${R}_{ \rm{ON,sp}}$ .